U.S. Pat. No. 5,456,760 teaches use an aqueous cleaning agent for removing soldering flux residue from an electrical assembly. The aqueous cleaning agent contains a high percentage of diacetonic alcohol. The aqueous cleaning agent optionally contains a small percentage of an alkali metal phosphate. The aqueous cleaning agent is agitated over the electrical assembly. Soldering flux residue is removed from the electrical assembly. The ""760 patent cites a patent application that discusses use of a small percentage of isopropanol, i.e. isopropyl alcohol, in a cleaning solution. The citation is in the fourth paragraph of column 1.
U.S. Pat. No. 5,269,850 teaches a composition, that contains an alkaline compound, for removing soldering flux residue from a substrate. The substrate is immersed into the composition.
U.S. Pat. No. 5,244,000 teaches spraying an aqueous cleaner, that contains an alkaline compound, onto a substrate, such as a printed wiring board, that has soldering flux residue on its surface. The ""000 patent teaches that 160 degree Fahrenheit aqueous cleaner is sprayed at 15 psi pressure onto a printed wiring board for 6 minutes. By spraying the substrate at 15 psi pressure with a relatively high temperature aqueous solution for relatively long period of time, soldering flux residue is removed from a printed wiring board. The teachings of U.S. Pat. No. 5,244,000 are incorporated herein by reference.
The present method uses a combination of steps to remove soldering flux residue from a substrate. The method including an alcohol immersion step, alcohol agitation steps and a spraying step with a basic aqueous cleaner, to remove soldering flux residue from a substrate, such as a printed wiring board. By using the present method, there is less of a chance of damage to electrical components, such as chip packages, on the substrate. By using the present method, soldering flux residue is removed from a substrate by spraying with the aqueous cleaner for less time and at a lower temperature than taught in U.S. Pat. No. 5,244,000. In the present method, an aqueous cleaner is sprayed for 1 minute or less. In the present method, the aqueous cleaner has a temperature of 130 degree Fahrenheit or less. A lower temperature and a shorter period of time, than in the ""000 patent, are achieved by using prior steps, wherein the substrate is immersed into pure commercial grade isopropyl alcohol and the pure commercial grade isopropyl alcohol is agitated, and a subsequent step, wherein the substrate is immersed into agitated pure commercial grade isopropyl alcohol. Thus the present method offers an improvement over the method taught by the prior art ""000 patent.
The present invention uses a combination of steps to completely removing soldering flux residues from a substrate, such as a printed wiring board.
In a first step, the substrate is immersed into pure commercial grade isopropyl alcohol. Soldering flux residue on the substrate is solvated by the pure commercial grade isopropyl alcohol.
In a second step, the pure commercial grade isopropyl alcohol is agitated by an agitator, for a period of time. The solvated soldering flux residue is broken apart by the agitated pure commercial grade isopropyl alcohol.
In a third step, a 130 degree Fahrenheit aqueous cleaner is sprayed at 15 psi pressure for 1 minute onto the substrate, to remove soldering flux residue from the substrate. The aqueous cleaner contains an alkaline compound.
In a fourth step, the substrate is placed in agitated pure commercial grade isopropyl alcohol to completely remove soldering flux residue from the substrate.
Thusly, soldering flux residue is removed from a substrate, such as a printed wiring board, by an improved method that uses a lower temperature and shorter spray time for an aqueous cleaner, than are used in the method of the ""000 prior art patent.
A method of removing soldering flux residue from a substrate comprising immersing the substrate into pure commercial grade isopropyl alcohol, the pure commercial grade isopropyl alcohol solvating the soldering flux residue, and spraying the substrate with an aqueous cleaner that contains an alkaline compound onto the substrate for 1 minute or less, the aqueous cleaner having a temperature of 130 degrees Fahrenheit or less, to remove soldering flux from the substrate.